Electromagnetic timing mechanism

ABSTRACT

A timing mechanism employs a rotary oscillatory member which is biased toward a neutral position and is pulsed electromagnetically in one direction about its axis so that it oscillates at a selected natural frequency. The timed oscillations of the member may be transformed into unidirectional motion of a second rotary member. This second member may then drive counting wheels which provide a visual indication of time as measured from a selected time base.

United States Patent 1 Pindell, Jr.

[54] ELECTROMAGNETIC TIMING MECHANISM [75] Inventor: Stuart M. Pindell,Jr., Winooski, Vt. [731 Assignee: Novox, Inc., Winooski, Vt.

221 Filedz Oct. 22, 1971 21 Appl. No.: 191,741

[52] 0.8. CI. ..58/23 D, 58/23 V, 58/23 R, 310/36 [51] Int. Cl ..G04c3/00, G04c 3/04 [58] Field of Search ..58/28 R, 23 D, 23 TF, 58/23 V,29-32; 310/36, 37, 38, 39', 318/134, 696

[56} References Cited UNITED STATES PATENTS 3,192,488 6/1965 Faith et al..310/36 X 3,214,662 10/1965 3,481,138 12/1969' Futagawaetal1......"58/28R 1 June 5, 1973 3,595,007 7/1971 Baker ..58/23 V 3,599,4208/1971 Oguey ..58/23 V 3,628,324 12/1971 Chopard et a1. ....58/23 D X3,221,191 11/1965 Cuches et a1 ..310/36 3,571,633 3/1971 Timmerman..310/36 X Primary Examiner-Richard B. Wilkinson AssistantExaminer-Stanley J. Witkowski Att0rneyCesari and McKenna [57] ABSTRACT Atiming mechanism employs a rotary oscillatory member which is biasedtoward a neutral position and is pulsed electromagnetically in onedirection about its axis so that it oscillates at a selected naturalfrequency. The timed oscillations of the member may be transformed intounidirectional motion of a second rotary member. This second member maythen drive counting wheels which provide a visual indication of time asmeasured from a selected time base.

31 Claims, 8 Drawing Figures PATENTEDJUM sums SHEET 1 [IF 6 PAIENTEUJUH51973 sum 5 or 6 j 227a 206 *1 Z gls FIG. 7

BACKGROUND OF THE INVENTION This invention relates to anelectromagnetically driven timing mechanism..-It relatesmoreparticularly to a mechanism ofthis type incorporating a mechanicaloscillatory member which is pulsed electromagnetically so that itoscillates at a selected natural frequency. The mechanism may indicatetime directly or it may perform various clocking and timing functions.

Electromagnetically driven mechanical oscillators generally are, ofcourse, well-known. Probably the most prevalent type is the tuning forkvibrator disclosed in US. Pat. No. 2,900,786 and related patents.Generally, these tuning fork oscillators operate at relatively highfrequencies and are relatively expensive to make. Also, they aresensitive to shock forces. Consequently, they are used primarily as thefrequency source in expensive time pieces which are not likely to besubjected to rugged use.

A second type of electromagnetically driven mechanical oscillator isused in very inexpensive clocks and display devices. Basically, thistype consists of a pendulum having a transverse arm attached to thependulum above the pivot point. This arm is made of a ferromagneticmaterial and extends into a wire coil. When a current pulse is appliedto the coil, the arm is repelled, causing the pendulum to swing in onedirection. The pendulum then swings in the opposite direction under theinfluence of gravity. The movement of the pendulum controls a switchwhich applies a current pulse to the coil each time the pendulum reachesthe end of its return swing. Thus, the oscillations of the pendulum aresustained as long as the current pulses are applied to the coil.

This latter type of vibrator is disadvantaged because it requires arelatively large volume to accommodate the swinging pendulum. Also, ithas a low mechanical 0. Therefore, its oscillation frequency is notparticularly accurate. Further, it is very susceptible to vibration andshock force. Another drawback of these prior low-frequency oscillatorysystems is the fact that their oscillations do not commenceautomatically when excitation pulses are applied. Rather, they must bestarted manually.

The problems noted above militate against the use of these prioroscillators as the control elements of elapsed time indicators withwhich we are particularly concerned here. These indicators are used onvehicles such as aircraft, tractors, boats and the like, to measureelapsed time for maintenance and warranty purposes. The indicatorshouldbe a relatively inexpensive throwaway item which is installed onthe vehicle and turned on when the vehicle is leased or purchased. Also,it is expected to run reliably for the life of the vehicle even thoughit is subjected to a variety of vibrational and shock forces. As apractical matter, then, conventional electromagnetically drivenoscillators are not used for this purpose. Rather, the indicators arecontrolled by conventional balance wheel timing mechanisms which arethemselves far from satisfactory for this purpose.

SUMMARY OF THE INVENTION Accordingly, this invention aims to provide anelectromagnetically driven mechanical oscillator having a relativelystable frequency. of oscillation.

Another object of the invention is to provide a me-- chanical oscillatorof this type having a relatively long die-down time (i.e. low rate ofdecay).

A further object of the invention is to provide a mechanical oscillatorof this type which starts automatically as soon as driving pulses areapplied.

A further object of the invention is to provide an electromagneticallydriven mechanical oscillator which requires a minimum amount ofexcitation energy.

Yet another object of the invention is to provide an oscillator of thistype having minimum internal energy losses. I

A further object is to provide an oscillator for a timing mechanismhaving a relatively high mechanical Q.

Still another object of this invention is to provide a timing mechanismwhich is powered by an electromagnetically driven mechanical oscillatorwhich is relatively immune to externally applied vibratory and shockforces.

A further object of the invention is to provide a timing mechanismcomposed of a unidirectional rotary member which is driven by theoscillator described above wherein there is a maximum amount of usefulenergy transferred between the oscillator and the rotary member.

Still another object of the invention is to provide a clock or elapsedtime indicator composed of the abovedescribed oscillator and rotarymember which has a relatively long, useful life.

Yet another object is to provide a timing mechanism which requires nomaintenance and is very inexpensive to make. I

Another object of the invention is to provide such an indicator which isrugged and reliable and capable of sustaining the violent shocks towhich it is subjected when installed on present-day, off-highwayequipment.

Other objects will in part be obvious and will in part appearhereinafter.

The invention accordingly comprises the features of construction,combination of elements and arrangement of parts which will beexemplified in the construction hereinafter set forth and the scope ofthe invention will be indicatedin the claims.

Briefly, the heart of the present timing mechanism is anelectromagnetically pulsed rotary oscillatory member. The mass of thismember is symmetrically disposed about a center point and spacedtherefrom so that the member has an appreciable moment of inertia. Themember is pivotally supported on a base and it is spring-biased toward aneutral position on its pivot.

In a preferred embodiment, the member is secured at its center of massto one end of a relatively stiff torsion spring which is anchored to thebase so that the member can oscillate about an axis coinciding with theaxis of the spring at a selected natural frequency. Thus, the springprovides both the support and bias for the oscillatory member.

The member is excited to oscillation by a brief magnetic force which isapplied to its periodically at a frequency approaching the naturalfrequency of the member. The application of this force is controlled bya sensing coil arrangement which senses the position of the member andgenerates an electrical signal. The signal is amplified and then used togenerate the pulsed magnetic force which drives the member. Thus, theexcitation force is applied at just the right instant to keep the memberoscillating at a selected, precise frequency.

cordingly, it is particularly suitable for use as a clock or frequencystandard in an electrical circuit to control the occurrence of events.Also, the movements of the oscillatory member can perform other timedfunctions. For example, a mirror affixed to the oscillatory member canperiodically reflect a light beam to a selected point. The same membercan be used to interrupt such a beam so that it, in effect, functions asa light chopper.

In the present instance, the oscillator is shown as part of a clock or,more particularly, an elapsed time indicator. Accordingly, the timingmechanism includes a motion transformer which converts the oscillatorymotion of the oscillatory member to unidirectional motion for actuatingthe clock movement. More particularly, the oscillatory member carries adriving pawl which engages the teeth of a ratchet wheel rotativelymounted adjacent the member. The amplitude of the oscillations of themember are within a range wherein the stroke of the pawl in a directionessentially tangent to the ratchet wheel is at least as great as thepitch of the ratchet teeth, but not greater than twice this pitch. Thus,each oscillation of the member causes the pawl to advance the ratchetwheel one tooth so that the rotational speed of the ratchet wheel isexactly proportional to the frequency of oscillation of the rotarymember. Since the oscillation frequency can be maintained quiteconstant, as noted above, therotational speed of the ratchet wheeldriven thereby is similarly stabilized.

The ratcheting mechanism also includes a retaining pawl which engagesthe ratchet teeth to prevent backup of the wheel. Ideally, the drivingand retaining pawls are arranged so that when the wheel is at rest, theretaining pawl butts a tooth of the wheel while the drive pawl liesapproximately halfway across a tooth. This insures that the driving pawland oscillatory member are lightly loaded initially so that, as soon asthe excitation pulses are applied, the member will start to oscillateautomatically and accelerate to maximum amplitude in a minimum time.This is particularly important in the case of an elapsed time incidatorbecause the unit must start reliably without any manual excitation ofthe oscillatory member and start driving the ratchet wheel immediatelyso that the indicator keeps accurate time.

The ratchet wheel is coupled through a gear reduction stage to a trainof counting wheels. Thus, continued rotation of the ratchet wheel causesthe counting wheels to display the time interval during which themechanism has been in operation. The presence of the gear reductionstage effectively decouples the oscillatory member from the counter sothat the presence of the counter wheels has no effect appreciable on theoscillator frequency.

The entire timing mechanism is supported within a sealed housing whichboth protects the mechanism from dust and the elements and alsoinsulates it to some extent from vibration and shock forces.Accordingly, the unit operates reliably for a relatively long periodeven under the most adverse conditions. Yet, the unit is inexpensive tomake and requires no maintenance.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of thenature and objects of the invention, reference should be had to thefollowing detailed description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is an isometric view of an elapsed time indicator embodying theprinciples of this invention;

FIG. 2 is a vertical sectional view with some parts shown in elevationof the FIG. 1 indicator;

FIG. 3 is a front elevational view with parts cut away thereof;

FIG. 4 is a sectional view along line 4-4 of FIG. 3;

FIG. 5 is a top view with parts cut away thereof;

FIG. 6 is a vertical sectional view like FIG. 2 of another embodiment ofthe invention;

FIG. 7 is a front elevational view with parts cutaway thereof; and

FIG. 8 is a top view with parts cut away thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIG. 1 of thedrawings, the components of the elapsed time indicator are contained ina rugged housing shown generally at 10 made of a suitable,impact-resistantmaterial such as metal, plastic or the like. Housing 10comprises a generally cylindrical casing 12 and a circular bezel 14. Theclock time is visible through a transparent window 16 supported by thebezel.

A set of six numbered wheels 18 mounted on a base plate 22 inside thehousing indicates the elapsed time. A slot 24 is provided in plate 22 sothat the numbers on these wheels are visible through the window.Depending upon the particular application, the wheels 18 can be gearedtogether so that they all indicate elapsed time in hours or the tworight-hand wheels can be arranged to indicate minutes with the remainingfour wheels showing elapsed hours.

A second slot 26 is provided in plate 22 to the right of slot 24. Aratchet wheel 28 carrying a bench mark 32 is visible through slot 26. Aslong as the indicator is operating, this fact is apparent by the benchmark 32 appearing in slot 26 every few seconds or so.

The indicator is designed to be mounted in a suitable opening in adashboard or other type of panel. This opening should be large enough toreceive casing 12. Bezel 14 is provided with a flange 38 arranged tooverhang the opening wall and holes 42 are provided in the flangethrough which screws may pass to secure the indicator to the panel.Alternatively, the indicator can be clamped to the panel in the mannerof conventional automobile clocks and accessories. In this event, theflange 38 can be made much narrower.

Turn now to FIGS. 2 and 3 which show one embodiment of the indicator.The moving parts of the mechanism are all contained inside the housing10. These comprise a mechanical oscillator shown generally at 46, amotion transformer indicated at 48, a gear reduction stage shown at 52and a counter section indicated at 54. All of these elements are mountedon two tabs 56 and 58 projecting out from the rear face of base plate 22(FIGS. 3 and 5). Furthermore, all of these components are situated alongonly two parallel axis between the two tabs.

Oscillator 46 comprises a rotary oscillatory member 62 which is mountednear one end of a relatively long,

stiff torsion spring 64, the other end of which is anchored in tab 58.The spring extends through a small central opening 66 at the center ofmember 62 with the spring and member being bonded at this point so thatthey rotate together. The opposite end of the spring is anchored to tab58 by being clamped between the top of the tab and a yoke 68 which ispressed down against the tabby screws 72. In order to prevent off-axisvibrations of the spring, its free end beyond member 62 is rotativelyreceived in an opening 74 in tab 56 (FIG. 5). The spring 64 issufficiently long that the rotary oscillations of the member are nottranslated to a vibrating mode.

Member 62 includes a pair of relatively massive portions 76 and 78symmetrically disposed on opposite sides of the axis A of spring 64.These portions are connected by a relatively narrow web- 82 containingthe opening 66. In the illustrated embodiment, member 62 is made ofbrass and its portions 76 and 78 are generally trapezoidal in shape forreasons to be discussed later. However, the member could just as well bemolded of plastic with weights being contained in portions 76 and 78.The'objective is simply to have appreciable mass spaced symmetricallyfrom axis A- so that the member 62 has a relatively high moment ofinertia.

With the member in the position shown in FIG. 2, spring 64 is in itsunstressed state. However, when the member is rotated through a smallangle in one direction or another about axis A, the spring winds up sothat it exerts a restoring force on the member, tending to return it toits FIG. 2 position. Accordingly, when so deflected, member 62 tends tooscillate about axis A at a natural frequency dependent upon its momentof inertia and the spring constant of spring 64.

Referring to FIGS. 2, 3 and 5 member 62 is excited to oscillationelectromagnetically. More particularly, a pair of discoid permanentmagnets 84 and 86 are recessed into the corresponding ends of 76a and78a of member portions 76 and 78. Further, a pair of drive coils 88 and92 are mounted opposite these magnets in openings 94 and 96 in a printedcircuit board 98. Board 98 carries an electronic drive circuit (notshown) which applies current pulses to coils 88 and 92 at timedintervals. Power is coupled to the drive circuit by way of terminals 99aand 99b'protruding from a raised boss 100 on the back of casing 12. Asuitable drive circuit is shown, for example, in the aforesaid U.S.patent.

A magnetic shunt, to wit a strip 102 of iron, extends between coils 88and 92 behind circuit board 98 so that the fields developed by coils 88and 92 are additive. Thus, when current pulses are applied to the coils88, a magnetic force couple is applied to member 62, causing it torotate in one direction, i.e. counterclockwise about axis A in FIG. 2.This causes the torsion spring 64 to wind up so that it biases themember 62 in the opposite direction, i.e. clockwise in FIG. 2.

We should mention that the end faces 76a and 78a of portions 76 and 78are cut on a bias, so that when these portions are closest to the coils,the magnets are parallel to the ends of the coils. This maximizes themagnetic forces coupled to the member.

The excitation pulses are applied while member 62 is engaged with anddrivingthe motion transformer 48 (FIG. 5). More particularly, a phasesensing coil 104 is situated adjacent coil 88. Each time member 62approaches the centerpoint of its clockwise rotation, the movement ofmagnet 84 induces a current pulse in coil 104. This current pulse isamplified and applied to the drive coils 88 and 92. Thus, the magneticpulses which drive member 62 are locked in phase with the oscillatorfrequency by sensing the position of the magnet 84. Actually, for bestresults, the natural frequency of the electronic drive circuit should besomewhat less than that of the frequency of the mechanical oscillator(e.g. percent) to be sure that the natural frequency of member 62 isdeterminitive of the oscillation frequency.

Because of its design, oscillator 46 has a relatively high Q. Also, itsoscillations decay very slowly when the excitation pulses cease. Thisenables the oscillator 46 itself to function as an accurate clock tocontrol various timing or sequencing operations. For example, part ofthe alternating current induced in sensing coil 104 when the system isoperating can be tapped off, amplified and used to generate triggerpulses for electronic control purposes. In another application, a mirrorindicated in dotted lines at 108 can be affixed to the oscillator endface 78b so that when a beam of light is reflected from mirror 108 to asurface, the beam is caused to scan across that surface at a controlledrate.

As best seen in FIG. 2, the motion transformer 48 converts theoscillatory motion of member 62 to unidirectional rotary motion. Thetransformer comprises the ratchet wheel 28 which is rotatively mountedon a shaft 110 whose ends are secured in tabs 56 and 58. Shaft 110 isparallel to spring 64 and is located directly in front of that spring.The ratchet wheel is made of a suitable, impact-resistant plastic suchas Delrin polyacetal and has a large number (e.g. 96) of small teeth 28aand it is perforated to minimize its weight. A driving pawl 112 isaffixed to member 62 and arranged to engage teeth 28a. Driving pawl 112is basically a relatively long, fiat, spring-like member which issecured to the end face 76b of member portion 76 by screws 114 or othersuitable means. The free end of pawl 112 rides on teeth 28a. That end isnotched at 112a (FIG. 5) with the teeth engaging the bottom of the notchso that the pawl cannot be displaced sideways and become disengaged fromteeth 28a whenthe device is subjected to shock.

The angle of face 76b, the pitch of teeth 28a and the arrangement of theratchet wheel and oscillator member are designed so that when the memberis at rest, the end of pawl 112 lies approximately half-way along one ofthe teeth 28a. Then, as the oscillator undergoes a full excursion in theclockwise direction, the pawl is carried beyond the end of that tooth.Then, when the oscillator commences counterclockwise rotation, the pawlengages that tooth and applies a force which is substan tiallytangential to the ratchet wheel. The pawl turns the wheel in thecounterclockwise direction a sufficient distance to enable the pawl to.engage behind the next tooth upon the second clockwise excursion of theoscillator member 62. p

A second, spring-like retaining pawl 118 similar in construction to pawl112 prevents backup of the ratchet wheel as the driving pawl isretracted to engage the next tooth. One end of the retaining pawl 118 issecured to plate 22 by suitable means such as screws 122. The free endof the pawl 118 is also notched at 118a and engages the ratchet wheelbeyond the point at which pawl 112 engages that wheel. The retainingpawl is oriented so that when the oscillator and ratchet wheel are atrest, its notched end 118a just butts against the rear face of a tooth28a.

When member 62 oscillates, ratchet wheel 28 moves in thecounterclockwise direction at a relatively rapid rate dependent upon theoscillator frequency. The bench mark 32 is painted or molded on the rimof the wheel so that one can easily observe the wheel in motion throughslot 26.

As best seen in FIGS. 3 and 5, a pinion gear 124 integral with wheel 28couples the rotary motion of the wheel to the gear reduction stage 52.Stage 52 comprises a train of spur gears rotatively mounted alternatelyon torsion spring 24 and shaft 110. A first gear 126 is mounted on thetorsion spring and driven by the gear 124 affixed to the ratchet wheel.Gear 126 includes an integral follower 128 which drives a second similargear 132 mounted on shaft 110. Gear 132 also includes an integrallyformed, coaxial follower 134 which drives a third gear 136 of similardesign mounted on torsion spring 24. Actually, the first two reductiongears 126-128 and 132-134 are identical, while the third reduction gear136-138 has a slightly different gear ratio.

The follower 138 meshes with a specially designed gear 142 mounted onshaft 110 shown specifically in FIG. 4. The side of gear 142 facing thecounter section 54 is formed with a pair of bosses 144 which project uptoward the torsion rod 24 spring 64. This gear is designed this way sothat a conventional off-the-shelf counter 54 can be used in themechanism. In other words, counter 54 is composed of standard counterwheels 54a-54f. These wheels are all mounted on shaft 110. The counteralso includes the usual pinion gears 152a-l52f to couple motion betweenthe individual wheels. These gears are all mounted on torsion spring 64.Also, conventionally, the first or least significant counter wheel 54ais turned by the first pinion gear 152a. Therefore, gear 142 is designedso that a boss 144 engages successive teeth of gear 152a duringsuccessive revolutions. In other words, for each revolution of gear 142,pinion gear 152a advances one tooth.

The illustrated mechanism is designed to indicate elapsed time in hours.Therefore, the gear ratios of the various gears in the gear reductionstage are arranged so that l hours operation of the oscillator willcause the least significant counter wheel 152a to advance one digit.

In this embodiment all of the moving components of the mechanism aremounted on torsion spring 64 and shaft 110. This enables the mechanismto be contained in a small, compact package; also, it facilitates itsassembly. We should mention, in addition, that the gears of thereduction stage and counter section which are mounted on the torsionspring are very lightweight and tend to float on the spring so that theyhave minimal effect on its twisting movements as member 62 oscillates.

The components of the timing mechanism are all assembled on base plate22. Window 16 is then seated in a circular groove 150 (FIG. 2) at therear of the bezel and sealed by epoxy resin or other suitable bondingagent. Then, the bezel is bonded to the front of base plate 22 with asimilar bonding agent. Finally, the casing 12 is bonded to the bezel andbase plate. The edge of the casing is provided with a circular lip 152which seats in the circular groove 154 at the rear of the bezel. Thecasing also has a circular flange 156 spaced from lip 152 which seats ina groove 158 in the rear of flange 38. A bonding agent is applied to thesurfaces of these mating parts so that the entire unit is sealed to keepout dust, dirt and moisture. The unit so packaged can withstand shocksas great as I000 gs and more. The housing itself contributes some ofthis shock resistance. Also, the tabs 56 and 58 which support theelements of the timing mechanism are somewhat resilient and furtherisolate the parts from external forces.

As soon. as current as applied to terminals 99a and 99b, member 62commences to oscillate with the amplitude of oscillation rapidlyreaching the point where the driving pawl 112 begins to index theratchet wheel 28. As noted above, the end of the driving pawl is restingapproximately half-way along one of the teeth of the ratchet wheel sothere is essentially no load on member 62 when current is applied.Therefore, the member can accelerate rapidly and reach its maximumamplitude of oscillation in a fraction of a second.

For best operation of the timing mechanism, the current pulses appliedto the drive coils 88 and 92 should be timed so that they are centeredon, or symmetrical with, the output load pulse (i.e. at the instant whenmember 62 through its pawl 112 is advancing the ratchet wheel 28). Thus,the driving pulses are applied at just the instant when member 62 isunder maximum load.

For illustrative purposes, we have shown the oscillator and ratchetwheel as driving a counter. However, it is obvious that the samearrangement could be used to turn other rotary members. For example, theratchet wheel can be geared to a disk having openings at various pointsin its surface. When the disk is positioned between a light source and aphotodetector, the arrangement of holes will permit light to betransmitted to the photodetector only at selected time intervals. Theoutput of the detector can then control any conventional device operatedon a time basis. For example, the device may take samples of theatmosphere periodically, etc. In a different application, the rotatingmember may be a polygonal mirror positioned in the path of a beam oflight. Rotation of the mirror would then cause a light beam to scansuccessively across a surface. Then, by suitably modulating the lightbeam, information could be displayed on that surface.

The present timing mechanism can also be powered by an alternatingcurrent supply. In this event, the natural frequency of the oscillatorybody is set to the frequency of the supply current and the supplyvoltage is applied directly to the electromagnet terminals. Thus, theoscillator is slaved to the supply current frequency at typicalvariations in that frequency of at least i 2 percent of the naturalfrequency of the oscillator. Of course, in this event, the phase sensingcoil and associated electronics are not required. Consequently, thismechanism used as an AC timer can be made less expensively than onewhich runs on direct current.

FIGS. 6 to 8 illustrate another embodiment of the timing mechanism whichis preferable when the torque needs to the ratchet wheel are relativelyhigh due to oscillator windage, hysteresis losses and the like. Also,this embodiment has an added advantage in that there is improveddecoupling of the oscillator and base, with the result that theos'cillatonoperates at a relatively high amplitude with low power input.As a consequence, the mechanism has a shorter start-up time and superioraccuracy.

This embodiment of the invention is similar in many respects to theFIGS. 1 to 5 embodiment. Consequently, for purposes of this description,we will dwell only on the main differences from the first embodiment.

This version of the mechanism has a base 202. The elements of themechanism are mounted on three parallel tabs 204, 206 and 208 affixed tobase 202. Tab 204 is supported on two pedestals 209a and 209b projectingout from the base and is situated near the middle of the base (FIG. 7).Tabs 206 and 208 are connected directly to the base and are spaced onopposite sides of tab 204. The mechanical oscillator shown generally at210 is comprised of a relatively long and stiff torsion spring 212 whichis secured at its midpoint to tab 204 approximately midway along thelength of the tab. Spring 212 has a raised portion 212a at its point ofattachment to tab 204 to provide a stronger point of engagement with thetab and to minimize stresses developed at the joint between the two.

A rotary oscillatory body 214 is secured at its center of mass to oneend of spring 212. Also, a second oscillatory member 216 is secured atits center of mass to the opposite end of spring 212. Each oscillatorybody has a relatively large mass which is located away from its centerof mass giving the body a relatively high moment of inertia. Body 214consists of a relatively long, flat, generally rectangular plate. Member216, on the other hand, is more or less discoid in shape. 1

When body 214 is displaced angularly, it tends to oscillate about theaxis of spring 212. Also, the other oscillatory member 216 oscillatesabout the same axis in sympathy. The system is arranged so that bothoscillatory members have substantially the same natural frequency ofoscillation. With this arrangement, the member 216 exerts acounterbalancing influence which results in reduced vibration beingtransmitted to base 202 as the oscillatoroscillates. In addition, thisreduced damping increases the efficiency of the oscillator andthe-accuracy of the timing mechanism as a whole.

A discoid permanent magnet 220 is mounted at one end of body 214. Theend of the body is notched at 214a so that the magnet is actuallyrecessed into the body. The oscillatory body also has a relatively longleg 2l4b located on the opposite side of the center of rotation of thebody and extending toward the base to compensate for the added mass onthe body due to magnet 220. A single driving coil 220 is supported by atab 224 connected to pedestal 209a (FIG. 7). 'Coil 222 is positioneddirectly opposite the magnet 220 and, when pulsed, tends to repel themagnet, causing the body 214 to rotate about its axis (i.e. spring 212).A printed circuit board 226 is supported by a pair of slotted pedestals227a and 227b above the spring 212 (FIG. 7). Board 226 carries asuitable electronic circuit to apply current pulses to coil 222 at theproper time to maintain body 214 in oscillation as described above.

As before, a phase sensing coil 228 is provided adjacent coil 222. Eachtime magnet 220 approaches the center point of its clockwise rotation(FIG. 6), a current is induced in coil 228 which is amplified andapplied to energize the drive coil 222 in the manner described above.

A ratchet wheel 232 is rotatively mounted on a shaft 234 whose ends aresecured to tabs 206 and 208 so that the shaft is positioned directly infront of the torsion spring 212. Also a spring-like pawl 236 is securedat one end by screws 238 or other suitable means to the forward edge ofbody 214 adjacent magnet 220. The free end 236a of the pawl is arrangedto engage the teeth of ratchet wheel 232 as described above inconnection with FIGS. 2-5. When body 214 oscillates, the pawl 236advances the ratchet wheel in the counterclockwise direction in FIG. 6.A retaining pawl 240 which is secured at one end to base 202 and whoseother end engages the ratchet wheel teeth prevents the wheel from'movingin the clockwise direction as the driving pawl 236 is retracted.

The ratchet wheel 232 carries a pinion gear 244 which couples the rotarymotion of the ratchet wheel to a gear reduction stage shown generally at246. The stage 246 is basically the same as the one disclosed in FIGS. 3and 5, except that the gears are not mounted on the same shafts whichsupport the ratchet wheel and oscillator body. Rather, the firstreduction gear 248 is mounted on a shaft 249 (FIG. 6) which is supportedby tabs 206 and 208 directly below the ratchet wheel shaft 234. Thisgear meshes with the pinion of the second reduction gear 252 which isrotatively supported by shaft 253. This shaft is supported by tabs 206and 208 directly behind shaft 249. The tab 204 is recessed at 204a toaccommodate the shaft (FIG. 6). The pinion of this gear meshes with thethird reduction gear 254 also mounted on shaft 249. Gear 254 is similarto gear 142 in that it is specially adapted to drive the pinion 256a ofa' conventional counter 256 (FIG. 8). This counter 256 is identical tocounter 54 in FIG. 5 and will not be further detailed here. Suffice itto say that the counter wheels of counter 256 are all mounted on shaft249 while the associated pinion gears are supported by shaft 253.Otherwise the counter operates in exactly the same way as counter 54,indicating the elapsed time through a window 260 in base 202.

When drive coil 222 is energized, body 214 oscillates about the axis ofspring 212 turning the ratchet wheel 232 in the counterclockwisedirection and, hence, incrementing the counter 256 at a controlled rate.We should mention at this point that a recess 214a is provided in body214 to provide clearance for shaft 253 when body 214 oscillates. Alsobody 216 is notched at 216a (FIG. 7) for the same reason. Thisembodiment of the invention has minimal energy losses and a relativelyhigh mechanical Q. Also, it is relatively independent of externallyapplied vibration and shock forces. Consequently, it is especiallysuitable as a clock or elapsed time indicator distined for use in anenvironment where these forces are present.

Actually, the present system is accurate enough and so inexpensive tomake-that it can be used as a substitute for present-day batter-operatedwall clocks and automobile clocks. Since the frequency of oscillator 46is quite constant and relatively temperature independent, the timeindication is much more accurate than that provided by present-dayinexpensive d.'c. operatedclocks.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes can be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in theaccompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed.

I claim:

1. A timing mechanism comprising A. a base,

B. a body C. means for rotatively mounting the body at its center ofmass to the base,

D. means for biasing the body so that it tends to assume a neutralposition about its axis of rotation said body having a moment of inertiawhich is high enough such that when the body is deflected from thisneutral position it tends to oscillate about its axis at its own naturalfrequency for a prolonged period of time, and

E. magnetic means for applying an off-axis force to the bodyperiodically so as to excite the body to and maintain it in oscillationabout its axis.

2. The timing mechanism defined in claim 1 wherein the biasing meansincludes a torsion spring connected between the base and the center ofrotation of the body.

3. The timing mechanism defined in claim 2 wherein A. one end of thetorsion spring is secured to the base, and

B. the body is secured near the free end of the spring.

4. The timing mechanism defined in claim 3 and further includingrestraining means for preventing the free end of the torsion spring fromvibrating off the spring axis 5. The timing mechanism defined in claim 2A. wherein l. a midportion of the torsion spring is secured to the base,and

2. the body is mounted adjacent one end of the torsion spring, and

B. further including a second body having a center of mass secured atsaid center adjacent the other end of the torsion spring, said secondbody tending to oscillate sympathetically with the other body.

6. The timing mechanism defined in claim 1 wherein the magnetic meanscomprise A. a ferromagnetic structure affixed to the body near the rimthereof,

B. means supported by the base for generating a pulsed electromagneticfield adjacent the ferromagnetic structure for producing the force whichopposes the biasing means, the frequency of the field pulses beingrelated to the natural oscillation frequency of the body.

7. The timing mechanism defined in claim 6 and further including A.means for sensing the phase of the oscillating body and producing anoutput signal in response thereto, and

B. means responsive to the output signal for exciting the fieldproducing means.

8. The timing mechanism defined in claim 7 wherein A. the phase sensingmeans is a wire coil in which a current is induced when the coil andferromagnetic structure are in close proximity and there is relativemovement between the two,

B. the exciting means is comprised of an amplifier which amplifies thecurrent signal from the phase sensing coil, and

C. the field producing means includes a wire coil which receives theamplified current signal from the amplifying means and generates amagnetic field in response thereto.

9. The timing mechanism defined in claim 1 and further including A. arotary member supported by the base, and

B. a motion transformer for converting the oscillatory motion of thebody to unidirectional motion of the rotary member.

10. The timing mechanism defined in claim 1 and further including A. aratchet wheel rotatively supported by the base in close proximity to theoscillatory body, and

B. a pawl secured to the body and in operative engagement with the teethofthe ratchet wheel for advancing the wheel when the body oscillates.

11. The timing mechanism defined in claim 10 and further including meansfor preventing rotation of the ratchet wheel in the direction oppositeto the direction in which it is driven by the pawl.

12. The timing mechanism defined in claim 9 and further including A. oneor more counter wheels rotatively supported by the base, and

B. means for coupling the rotary motion of the rotary member to acounter wheel.

13. The timing mechanism defined in claim 12 wherein A. The biasingmeans is a torsion spring which also supports the body, and

B. the counter wheels are rotatively mounted on the torsion spring.

14. The timing mechanism defined in claim l2 wherein the coupling meansinclude one or more gears operating between the rotary memberand thecounter wheels so that a selected number of rotations of the rotarymember produce a different selected number of rotations of the wheel.

15. A timing mechanism comprising A. a base,

B. a body having a center of mass,

C. a torsion spring connected at one point on its length to the base andat a second point on its length to the body at its center of mass sothat when the body is rotated about 'its center, the spring winds up andexerts a restoring bias on the body, with the result that the body has aselected natural frequency of oscillation D. a magnet mounted on thebody near its rim,

E. a second magnet supported by the base so that it is opposite thefirst magnet, at least one of the magnets being an electromagnet,

F means for energizing the electromagnet periodically when the body isoriented at a selected angular position about its center of rotation sothat the body is maintained in oscillation.

16. The timing mechanism defined in claim 15 and including A. anadditional magnet mounted on the body near its rim, said additionalmagnet being symmetrically disposed about the center of mass of the bodywith respect to the first magnet, and

B. a fourth magnet supported by the base opposite the third magnet, atleast one of the third and fourth magnets being a second electromagnet,said second electromagnet operating in coincidence further includingmeans operatively associatedv with one of the oscillatory bodies forcontrolling the time of occurrence of an event.

wherein the driven means include reduction gears.

with the other electromagnet to help maintain the body in oscillation.17. The timing mechanism defined in claim 15 A. wherein,

l. the torsion spring is supported near its mid-point by the base, and2. further including a second body supported at its center of massadjacent the other end of the torsion spring so that it oscillatessympathetically with the other body. 18. The timing mechanism defined inclaim 17 wherein the natural frequencies of oscillation of the twobodies are comparable.

19. The timing mechanism defined in claim and 15 20. The timingmechanism defined in claim 15 and further including A. a ratchet wheellocated relatively near the body 20 wherein A. said edge of the pawl isnotched, and B. the ratchet wheel teeth engage the bottom of the notch.

22. The timing mechanism defined in claim 20 wherein the oppositerotation preventing means include a retaining pawl supported by the baseand having an edge engaging the ratchet wheel teeth when the drivingpawl is retracted by the oscillatory body.

23. The timing mechanism defined in claim 22 and further including A.means defining a window in the base adjacent the rim of the ratchetwheel, and I B. indicia on the ratchet wheel rim which appears in thewindow periodically as the ratchet wheel rotates.

24. The timing mechanism defined in claim 20 wherein the edge of thedriving pawl moves tangentially to the ratchet wheel when it advancesthe wheel in the given direction as the body oscillates.

25. The timing mechanism defined in claim 20 and further A. including acounter supported by the base, and

B. means driven by the ratchet wheel for increment- .ing the counter.

26. The timing mechanism defined in claim 25 and further including A. awindow in the base adjacent the counter through which the numerals onthe counter are apparent, B. a casing enclosing all of the recitedtiming mechanism components, and C. means for securing the casing to thebase. 27. The timing mechanism defined in claim 25 28. The timingmechanism defined in claim 15 wherein the energizing means include A. asensing coil supported on one of the base and the body in which acurrent signal is induced when it is in close moving proximity to themagnet on the other of the base and the body, and

B. a switch responsive to the current signal in the sensing coil forcontrolling the energization of the electromagnet so that the body ispulsed magnetically at a controlled rate dependent primarily on thenatural oscillation frequency of the body.

29. The timing mechanism defined in claim 28 0 wherein the energizingmeans also include an amplifier for amplifying the current signal in thesensing coil prior to its application to the switch.

30. The timing mechanism defined in claim 28 wherein the electromagnetis pulsed as the body is advancing the ratchet wheel in the givendirection.

31. A timing mechanism comprising A. a base,

B. a torsion spring,

C. means for securing the torsion spring near its midpoint to the base,

D. a body secured at its center of mass adjacent one end of the torsionspring, said body tending to oscillate about its center of mass at aselected natural frequency,

E. a second body secured at its center of mass adjacent the opposite endof the torsion spring, said second body tending to oscillatesympathetically with the first body at a selected natural frequency,

F. a first magnet secured to one of the bodies near its rim,

0. a second magnet supported by the base near the first magnet, at leastone of said magnets being an electromagnet,

l-l. means for energizing the electromagnet so that it reacts with theother magnet and tends to angularly deflect the attached body about itscenter of mass,

1. means for controlling the energizing of the electromagnet so that theelectromagnet is pulsed momentarily when the body is at a selectedangular position about its center of mass so as to maintain the body inoscillation, said controlling means including 1. a phase sensing coil inwhich signal is induced when the coil is in ,close moving proximity witha magnet, and 2. a switch responsive to the current signal forcontrolling the power applied to the electromagnet,

J. a ratchet wheel rotativly supported by the base in close proximity tothe body,

K. a pawl secured to the body and having an edge arranged to engage theteeth of the ratchet wheel and advance the wheel in a given directionwhen the body oscillates,

L. A retaining pawl supported by the base and having an edge arranged toengage the ratchet wheel teeth to prevent the wheel from moving in adirection opposite to the given direction,

M. a counter supported by the base,

N. reduction gears driven by the ratchet wheel for incrementing thecounter at a controlled rate as the body oscillates,

O. a window in the base adjacent the counter through which the numbersdisplayed by the counter may be observed,

P. A housing protectively enclosing the moving components of the timingmechanism, said housing being secured to the base, and

Q. means on the outside of the housing for conducting an electricalcurrent to the electromagnet inside the housing.

1. A timing mechanism comprising A. a base, B. a body C. means forrotatively mounting the body at its center of mass to the base, D. meansfor biasing the body so that it tends to assume a neutral position aboutits axis of rotation said body having a moment of inertia which is highenough such that when the body is deflected from this neutral positionit tends to oscillate about its axis at its own natural frequency for aprolonged period of time, and E. magnetic means for applying an off-axisforce to the body periodically so as to excite the body to and maintainit in oscillation about its axis.
 2. The timing mechanism defined inclaim 1 wherein the biasing means includes a torsion spring connectedbetween the base and the center of rotation of the body.
 2. the body ismounted adjacent one end of the torsion spring, and B. further includinga second body having a center of mass secured at said center adjacentthe other end of the torsion spring, said second body tending tooscillate sympathetically with the other body.
 2. a switch responsive tothe current signal for controlling the power applied to theelectromagnet, J. a ratchet wheel rotatively supported by the base inclose proximity to the body, K. a pawl secured to the body and having anedge arranged to engage the teeth of the ratchet wheel and advance thewheel in a given direction when the body oscillates, L. A retaining pawlsupported by the base and having an edge arranged to engage the ratchetwheel teeth to prevent the wheel from moving in a direction opposite tothe given direction, M. a counter supported by the base, N. reductiongears driven by the ratchet wheel for incrementing the counter at acontrolled rate as the body oscillates, O. a window in the base adjacentthe counter through which the numbers displayed by the counter may beobserved, P. A housing protectively enclosing the moving components ofthe timing mechanism, said housing being secured to the base, and Q.means on the outside of the housing for conducting an electrical currentto the electromagnet inside the housing.
 2. further including a secondbody supported at its center of mass adjacent the other end of thetorsion spring so that it oscillates sympathetically with the otherbody.
 3. The timing mechanism defined in claim 2 wherein A. one end ofthe torsion spring is secured to the base, and B. the body is securednear the free end of the spring.
 4. The timing mechanism defined inclaim 3 and further including restraining means for preventing the freeend of the torsion spring from vibrating off the spring axis
 5. Thetiming mechanism defined in claim 2 A. wherein
 6. The timing mechanismdefined in claim 1 wherein the magnetic means comprise A. aferromagnetic structure affixed to the body near the rim thereof, B.means supported by the base for generating a pulsed electromagneticfield adjacent the ferromagnetic structure for producing the force whichopposes the biasing means, the frequency of the field pulses beingrelated to the natural oscillation frequency of the body.
 7. The timingmechanism defined in claim 6 and further includingA. means for sensingthe phase of the oscillating body and producing an output signal inresponse thereto, and B. means responsive to the output signal forexciting the field producing means.
 8. The timing mechanism defined inclaim 7 wherein A. the phase sensing means is a wire coil in which acurrent is induced when the coil and ferromagnetic structure are inclose proximity and there is relative movement between the two, B. theexciting means is comprised of an amplifier which amplifies the currentsignal from the phase sensing coil, and C. the field producing meansincludes a wire coil which receives the amplified current signal fromthe amplifying means and generates a magnetic field in response thereto.9. The timing mechanism defined in claim 1 and further including A. arotary member supported by the base, and B. a motion transformer forconverting the oscillatory motion of the body to unidirectional motionof the rotary member.
 10. The timing mechanism defined in claim 1 andfurther including A. a ratchet wheel rotatively supported by the base inclose proximity to the oscillatory body, and B. a pawl secured to thebody and in operative engagement with the teeth of the ratchet wheel foradvancing the wheel when the body oscillates.
 11. The timing mechanismdefined in claim 10 and further including means for preventing rotationof the ratchet wheel in the direction opposite to the direction in whichit is driven by the pawl.
 12. The timing mechanism defined in claim 9and further including A. one or more counter wheels rotatively supportedby the base, and B. means for coupling the rotary motion of the rotarymember to a counter wheel.
 13. The timing mechanism defined in claim 12wherein A. The biasing means is a torsion spring which also supports thebody, and B. the coUnter wheels are rotatively mounted on the torsionspring.
 14. The timing mechanism defined in claim 12 wherein thecoupling means include one or more gears operating between the rotarymember and the counter wheels so that a selected number of rotations ofthe rotary member produce a different selected number of rotations ofthe wheel.
 15. A timing mechanism comprising A. a base, B. a body havinga center of mass, C. a torsion spring connected at one point on itslength to the base and at a second point on its length to the body atits center of mass so that when the body is rotated about its center,the spring winds up and exerts a restoring bias on the body, with theresult that the body has a selected natural frequency of oscillation D.a magnet mounted on the body near its rim, E. a second magnet supportedby the base so that it is opposite the first magnet, at least one of themagnets being an electromagnet, F. means for energizing theelectromagnet periodically when the body is oriented at a selectedangular position about its center of rotation so that the body ismaintained in oscillation.
 16. The timing mechanism defined in claim 15and including A. an additional magnet mounted on the body near its rim,said additional magnet being symmetrically disposed about the center ofmass of the body with respect to the first magnet, and B. a fourthmagnet supported by the base opposite the third magnet, at least one ofthe third and fourth magnets being a second electromagnet, said secondelectromagnet operating in coincidence with the other electromagnet tohelp maintain the body in oscillation.
 17. The timing mechanism definedin claim 15 A. wherein,
 18. The timing mechanism defined in claim 17wherein the natural frequencies of oscillation of the two bodies arecomparable.
 19. The timing mechanism defined in claim 15 and furtherincluding means operatively associated with one of the oscillatorybodies for controlling the time of occurrence of an event.
 20. Thetiming mechanism defined in claim 15 and further including A. a ratchetwheel located relatively near the body and arranged so that its facesare in planes lying parallel to the plane of rotation of the body, B. aflexible resilient driving pawl secured to the body, said pawl having anedge arranged to engage the teeth of the ratchet wheel so as to turn thewheel in a given direction when the body oscillates, and C. means forpreventing the wheel from turning in the direction opposite to the givendirection.
 21. The timing mechanism defined in claim 20 wherein A. saidedge of the pawl is notched, and B. the ratchet wheel teeth engage thebottom of the notch.
 22. The timing mechanism defined in claim 20wherein the opposite rotation preventing means include a retaining pawlsupported by the base and having an edge engaging the ratchet wheelteeth when the driving pawl is retracted by the oscillatory body. 23.The timing mechanism defined in claim 22 and further including A. meansdefining a window in the base adjacent the rim of the ratchet wheel, andB. indicia on the ratchet wheel rim which appears in the windowperiodically as the ratchet wheel rotates.
 24. The timing mechanismdefined in claim 20 wherein the edge of the driving pawl movestangentially to the ratchet wheel when it advances the wheel in thegiven direction as the body oscillates.
 25. The timing mechanism definedin claim 20 and further A. including a counter supported by the base,and B. means driven by the ratchet wheel for incrementing the counter.26. The timing mechanism defined in claim 25 and further including A. Awindow in the base adjacent the counter through which the numerals onthe counter are apparent, B. a casing enclosing all of the recitedtiming mechanism components, and C. means for securing the casing to thebase.
 27. The timing mechanism defined in claim 25 wherein the drivenmeans include reduction gears.
 28. The timing mechanism defined in claim15 wherein the energizing means include A. a sensing coil supported onone of the base and the body in which a current signal is induced whenit is in close moving proximity to the magnet on the other of the baseand the body, and B. a switch responsive to the current signal in thesensing coil for controlling the energization of the electromagnet sothat the body is pulsed magnetically at a controlled rate dependentprimarily on the natural oscillation frequency of the body.
 29. Thetiming mechanism defined in claim 28 wherein the energizing means alsoinclude an amplifier for amplifying the current signal in the sensingcoil prior to its application to the switch.
 30. The timing mechanismdefined in claim 28 wherein the electromagnet is pulsed as the body isadvancing the ratchet wheel in the given direction.
 31. A timingmechanism comprising A. a base, B. a torsion spring, C. means forsecuring the torsion spring near its midpoint to the base, D. a bodysecured at its center of mass adjacent one end of the torsion spring,said body tending to oscillate about its center of mass at a selectednatural frequency, E. a second body secured at its center of massadjacent the opposite end of the torsion spring, said second bodytending to oscillate sympathetically with the first body at a selectednatural frequency, F. a first magnet secured to one of the bodies nearits rim, G. a second magnet supported by the base near the first magnet,at least one of said magnets being an electromagnet, H. means forenergizing the electromagnet so that it reacts with the other magnet andtends to angularly deflect the attached body about its center of mass,I. means for controlling the energizing of the electromagnet so that theelectromagnet is pulsed momentarily when the body is at a selectedangular position about its center of mass so as to maintain the body inoscillation, said controlling means including